Dual-beam X-ray nano-holotomography.

Nanotomography with hard X-rays is a widely used technique for high-resolution imaging, providing insights into the structure and composition of various materials. In recent years, tomographic approaches based on simultaneous illuminations of the same sample region from different angles by multiple beams have been developed at micrometre image resolution. Transferring these techniques to the nanoscale is challenging due to the loss in photon flux by focusing the X-ray beam. We present an approach for multi-beam nanotomography using a dual-beam Fresnel zone plate (dFZP) in a near-field holography setup. The dFZP generates two nano-focused beams that overlap in the sample plane, enabling the simultaneous acquisition of two projections from slightly different angles. This first proof-of-principle implementation of the dual-beam setup allows for the efficient removal of ring artifacts and noise using machine-learning approaches. The results open new possibilities for full-field multi-beam nanotomography and pave the way for future advancements in fast holotomography and artifact-reduction techniques.

Advancements in Liquid Jet Technology and X-ray Spectroscopy for Understanding Energy Conversion Materials during Operation.

ConspectusWater splitting is intensively studied for sustainable and effective energy storage in green/alternative energy harvesting-storage-release cycles. In this work, we present our recent developments for combining liquid jet microtechnology with different types of soft X-ray spectroscopy at high-flux X-ray sources, in particular developed for studying the oxygen evolution reaction (OER). We are particularly interested in the development of in situ photon-in/photon-out techniques, such as in situ resonant inelastic X-ray scattering (RIXS) techniques at high-repetition-frequency X-ray sources, pointing toward operando capabilities. The pilot catalytic systems we use are perovskites having the general structure ABO3 with lanthanides or group II elements at the A sites and transition metals at the B sites. Depending on the chemical substitutions of ABO3, their catalytic activity for OER can be tuned by varying the composition.In this work, we present our in situ RIXS studies of the manganese L-edge of perovskites during OER. We have developed various X-ray spectroscopy approaches like transmission zone plate-, reflection zone plate-, and grating-based emission spectroscopy techniques. Combined with tunable incident X-ray energies, we yield complementary information about changing (inverse) X-ray absorption features of the perovskites, allowing us to deduce element- and oxidation-state-specific chemical monitoring of the catalyst. Adding liquid jet technology, we monitor element- and oxidation-state-specific interactions of the catalyst with water adsorbate during OER. By comparing the different technical spectroscopy approaches combined with high-repetition-frequency experiments at synchrotrons and free-electron lasers, we conclude that the combination of liquid jet with low-resolution zone-plate-based X-ray spectroscopy is sufficient for element- and oxidation-state-specific chemical monitoring during OER and easy to handle.For an in-depth study of OER mechanisms, however, including the characterization of catalyst-water adsorbate in terms of their charge transfer properties and especially valence intermediates formed during OER, high-resolution spectroscopy tools based on a combination of liquid jets with gratings bear bigger potential since they allow resolution of otherwise-overlapping X-ray spectroscopy transitions. Common for all of these experimental approaches is the conclusion that without the versatile developments of liquid jets and liquid beam technologies, elaborate experiments such as high-repetition experiments at high-flux X-ray sources (like synchrotrons or free-electron lasers) would hardly be possible. Such experiments allow sample refreshment for every single X-ray shot for repetition frequencies of up to 5 MHz, so that it is possible (a) to study X-ray-radiation-sensitive samples and also (b) to utilize novel types of flux-hungry X-ray spectroscopy tools like photon-in/photon-out X-ray spectroscopy to study the OER.

Interplay of Andreev Reflection and Coulomb Blockade in Hybrid Superconducting Single-Electron Transistors.

We study the interplay between Coulomb blockade and superconductivity in a tunable superconductor-superconductor-normal-metal single-electron transistor. The device is realized by connecting the superconducting island via an oxide barrier to the normal-metal lead and with a break junction to the superconducting lead. The latter enables Cooper pair transport and (multiple) Andreev reflection. We show that these processes are relevant also far above the superconducting gap and that signatures of Coulomb blockade may reoccur at high bias while they are absent for small bias in the strong-coupling regime. Our experimental findings agree with simulations using a rate equation approach in combination with the full counting statistics of multiple Andreev reflection.

Hard X-ray full-field nanoimaging using a direct photon-counting detector.

Full-field X-ray nanoimaging is a widely used tool in a broad range of scientific areas. In particular, for low-absorbing biological or medical samples, phase contrast methods have to be considered. Three well established phase contrast methods at the nanoscale are transmission X-ray microscopy with Zernike phase contrast, near-field holography and near-field ptychography. The high spatial resolution, however, often comes with the drawback of a lower signal-to-noise ratio and significantly longer scan times, compared with microimaging. In order to tackle these challenges a single-photon-counting detector has been implemented at the nanoimaging endstation of the beamline P05 at PETRA III (DESY, Hamburg) operated by Helmholtz-Zentrum Hereon. Thanks to the long sample-to-detector distance available, spatial resolutions of below 100 nm were reached in all three presented nanoimaging techniques. This work shows that a single-photon-counting detector in combination with a long sample-to-detector distance allows one to increase the time resolution for in situ nanoimaging, while keeping a high signal-to-noise level.

Refractive axicon for X-ray microscopy applications: design, optimization, and experiment.

In a full-field transmission X-ray microscopy (TXM) setup, a condenser X-ray optical element is used to illuminate the sample by condensing the X-ray beam delivered by the synchrotron storage ring. On-going and future upgrades of synchrotron facilities to diffraction-limited storage rings will pose new challenges to these TXM setups, such as much smaller X-ray beams on the condenser. Here, we demonstrate that a refractive axicon can be used as an X-ray beam shaper to match the ring-shaped aperture of the condenser. Aiming at more efficient use of the incoming X-ray intensity, we explore several axicon designs both analytically and with numerical simulations. The axicons were produced by two-photon polymerization 3D printing on thin silicon nitride membrane substrates. The first characterization of the axicon was carried out at the TOMCAT beamline of the Swiss Light Source (Switzerland).

Hard X-ray stereographic microscopy for single-shot differential phase imaging.

The characterisation of fast phenomena at the microscopic scale is required for the understanding of catastrophic responses of materials to loads and shocks, the processing of materials by optical or mechanical means, the processes involved in many key technologies such as additive manufacturing and microfluidics, and the mixing of fuels in combustion. Such processes are usually stochastic in nature and occur within the opaque interior volumes of materials or samples, with complex dynamics that evolve in all three dimensions at speeds exceeding many meters per second. There is therefore a need for the ability to record three-dimensional X-ray movies of irreversible processes with resolutions of micrometers and frame rates of microseconds. Here we demonstrate a method to achieve this by recording a stereo phase-contrast image pair in a single exposure. The two images are combined computationally to reconstruct a 3D model of the object. The method is extendable to more than two simultaneous views. When combined with megahertz pulse trains of X-ray free-electron lasers (XFELs) it will be possible to create movies able to resolve 3D trajectories with velocities of kilometers per second.

Compact single-shot soft X-ray photon spectrometer for free-electron laser diagnostics.

The photon spectrum from free-electron laser (FEL) light sources offers valuable information in time-resolved experiments and machine optimization in the spectral and temporal domains. We have developed a compact single-shot photon spectrometer to diagnose soft X-ray spectra. The spectrometer consists of an array of off-axis Fresnel zone plates (FZP) that act as transmission-imaging gratings, a Ce:YAG scintillator, and a microscope objective to image the scintillation target onto a two-dimensional imaging detector. This spectrometer operates in segmented energy ranges which covers tens of electronvolts for each absorption edge associated with several atomic constituents: carbon, nitrogen, oxygen, and neon. The spectrometer's performance is demonstrated at a repetition rate of 120 Hz, but our detection scheme can be easily extended to 200 kHz spectral collection by employing a fast complementary metal oxide semiconductor (CMOS) line-scan camera to detect the light from the scintillator. This compact photon spectrometer provides an opportunity for monitoring the spectrum downstream of an endstation in a limited space environment with sub-electronvolt energy resolution.

Litigation associated with 5-alpha-reductase-inhibitor use: A Canadian legal database review.

INTRODUCTION: 5α-reductase inhibitors (5ARI) are commonly prescribed medications. There is ongoing controversy about the adverse events of these medications. The aim of this study is to characterize lawsuits in Canada involving medical complications of 5ARIs use. MATERIALS AND METHODS: Legal cases were queried from CanLII. Cases were included if they involved a party taking a 5ARI who alleged an adverse event. Relevant full cases were retained, and pertinent characteristics were extracted with the help of a legal expert. RESULTS: Our deduplicated search yielded 67 unique legal documents from December 2013 to February 2019. Twelve of these documents met the inclusion criteria (representing 3 cases, considering each case had several hearings). The medical complaints filed by the plaintiffs were all related to medication side effects (n = 3, 100%). The plaintiffs were commonly patients themselves. Defendants were exclusively pharmaceutical companies. Persistent erectile dysfunction after stopping the medication was cited as a side effect in all complaints. The prescriptions were made for male pattern hair loss (n = 3, 100%) in all cases. All cases represent class actions brought by the plaintiffs, and they have been certified by their respective court. However, the cases are still ongoing. CONCLUSION: While 5ARI use has been linked to undesired sexual side effects, there have been few litigations on this issue in Canada. Persisting sexual dysfunction after stopping the medication is the only complaint presented in legal action. To date, no judgment against a physician or pharmaceutical company was identified. Cases are still ongoing.

Optimizing the energy bandwidth for transmission full-field X-ray microscopy experiments.

Full-field transmission X-ray microscopy (TXM) is a very potent high-resolution X-ray imaging technique. However, it is challenging to achieve fast acquisitions because of the limited efficiency of the optics. Using a broader energy bandwidth, for example using a multilayer monochromator, directly increases the flux in the experiment. The advantage of more counts needs to be weighed against a deterioration in achievable resolution because focusing optics show chromatic aberrations. This study presents theoretical considerations of how much the resolution is affected by an increase in bandwidth as well as measurements at different energy bandwidths (ΔE/E = 0.013%, 0.27%, 0.63%) and the impact on achievable resolution. It is shown that using a multilayer monochromator instead of a classical silicon double-crystal monochromator can increase the flux by an order of magnitude with only a limited effect on the resolution.

Rapid aberration correction for diffractive X-ray optics by additive manufacturing.

Diffraction-limited hard X-ray optics are key components for high-resolution microscopy, in particular for upcoming synchrotron radiation sources with ultra-low emittance. Diffractive optics like multilayer Laue lenses (MLL) have the potential to reach unprecedented numerical apertures (NA) when used in a crossed geometry of two one-dimensionally focusing lenses. However, minuscule fluctuations in the manufacturing process and technical limitations for high NA X-ray lenses can prevent a diffraction-limited performance. We present a method to overcome these challenges with a tailor-made refractive phase plate. With at-wavelength metrology and a rapid prototyping approach we demonstrate aberration correction for a crossed pair of MLL, improving the Strehl ratio from 0.41(2) to 0.81(4) at a numerical aperture of 3.3 × 10-3. This highly adaptable aberration-correction scheme provides an important tool for diffraction-limited hard X-ray focusing.

Slope error correction on X-ray reflection gratings by a variation of the local line density.

The patterning of x-ray grating surfaces by electron-beam lithography offers large flexibility to realize complex optical functionalities. Here, we report on a proof-of-principle experiment to demonstrate the correction of slope errors of the substrates by modulating the local density of the grating lines. A surface error map of a test substrate was determined by optical metrology and served as the basis for an aligned exposure of a corrected grating pattern made by electron-beam lithography. The correction is done by a variation of the local line density in order to compensate for the local surface error. Measurements with synchrotron radiation and simulations in the soft X-ray range confirm that the effects of slope errors were strongly reduced over an extended wavelength range.

Observation of Magnetic Helicoidal Dichroism with Extreme Ultraviolet Light Vortices.

We report on the experimental evidence of magnetic helicoidal dichroism, observed in the interaction of an extreme ultraviolet vortex beam carrying orbital angular momentum with a magnetic vortex. Numerical simulations based on classical electromagnetic theory show that this dichroism is based on the interference of light modes with different orbital angular momenta, which are populated after the interaction between light and the magnetic topology. This observation gives insight into the interplay between orbital angular momentum and magnetism and sets the framework for the development of new analytical tools to investigate ultrafast magnetization dynamics.

Light-Induced Magnetization at the Nanoscale.

Triggering and switching magnetic moments is of key importance for applications ranging from spintronics to quantum information. A noninvasive ultrafast control at the nanoscale is, however, an open challenge. Here, we propose a novel laser-based scheme for generating atomic-scale charge current loops within femtoseconds. The associated orbital magnetic moments remain ferromagnetically aligned after the laser pulses have ceased and are localized within an area that is tunable via laser parameters and can be chosen to be well below the diffraction limit of the driving laser field. The scheme relies on tuning the phase, polarization, and intensities of two copropagating Gaussian and vortex laser pulses, allowing us to control the spatial extent, direction, and strength of the atomic-scale charge current loops induced in the irradiated sample upon photon absorption. In the experiment we used He atoms driven by an ultraviolet and infrared vortex-beam laser pulses to generate current-carrying Rydberg states and test for the generated magnetic moments via dichroic effects in photoemission. Ab initio quantum dynamic simulations and analysis confirm the proposed scenario and provide a quantitative estimate of the generated local moments.

Spectral monitoring at SwissFEL using a high-resolution on-line hard X-ray single-shot spectrometer.

The performance and parameters of the online photon single-shot spectrometer (PSSS) at the Aramis beamline of the SwissFEL free-electron laser are presented. The device operates between the photon energies 4 and 13 keV and uses diamond transmission gratings and bent Si crystals for spectral measurements on the first diffraction order of the beam. The device has an energy window of 0.7% of the median photon energy of the free-electron laser pulses and a spectral resolution (full width at half-maximum) ΔE/E on the order of 10-5. The device was characterized by comparing its performance with reference data from synchrotron sources, and a parametric study investigated other effects that could affect the reliability of the spectral information.

High-speed fixed-target serial virus crystallography.

We report a method for serial X-ray crystallography at X-ray free-electron lasers (XFELs), which allows for full use of the current 120-Hz repetition rate of the Linear Coherent Light Source (LCLS). Using a micropatterned silicon chip in combination with the high-speed Roadrunner goniometer for sample delivery, we were able to determine the crystal structures of the picornavirus bovine enterovirus 2 (BEV2) and the cytoplasmic polyhedrosis virus type 18 polyhedrin, with total data collection times of less than 14 and 10 min, respectively. Our method requires only micrograms of sample and should therefore broaden the applicability of serial femtosecond crystallography to challenging projects for which only limited sample amounts are available. By synchronizing the sample exchange to the XFEL repetition rate, our method allows for most efficient use of the limited beam time available at XFELs and should enable a substantial increase in sample throughput at these facilities.

Measurement and compensation of misalignment in double-sided hard X-ray Fresnel zone plates.

Double-sided Fresnel zone plates are diffractive lenses used for high-resolution hard X-ray microscopy. The double-sided structures have significantly higher aspect ratios compared with single-sided components and hence enable more efficient imaging. The zone plates discussed in this paper are fabricated on each side of a thin support membrane, and the alignment of the zone plates with respect to each other is critical. Here, a simple and reliable way of quantifying misalignments by recording efficiency maps and measuring the absolute diffraction efficiency of the zone plates as a function of tilting angle in two directions is presented. The measurements are performed in a setup based on a tungsten-anode microfocus X-ray tube, providing an X-ray energy of 8.4 keV through differential measurements with a Cu and an Ni filter. This study investigates the sources of the misalignments and concludes that they can be avoided by decreasing the structure heights on both sides of the membrane and by pre-programming size differences between the front- and back-side zone plates.

Pushing the temporal resolution in absorption and Zernike phase contrast nanotomography: enabling fast in situ experiments.

Hard X-ray nanotomography enables 3D investigations of a wide range of samples with high resolution (<100 nm) with both synchrotron-based and laboratory-based setups. However, the advantage of synchrotron-based setups is the high flux, enabling time resolution, which cannot be achieved at laboratory sources. Here, the nanotomography setup at the imaging beamline P05 at PETRA III is presented, which offers high time resolution not only in absorption but for the first time also in Zernike phase contrast. Two test samples are used to evaluate the image quality in both contrast modalities based on the quantitative analysis of contrast-to-noise ratio (CNR) and spatial resolution. High-quality scans can be recorded in 15 min and fast scans down to 3 min are also possible without significant loss of image quality. At scan times well below 3 min, the CNR values decrease significantly and classical image-filtering techniques reach their limitation. A machine-learning approach shows promising results, enabling acquisition of a full tomography in only 6 s. Overall, the transmission X-ray microscopy instrument offers high temporal resolution in absorption and Zernike phase contrast, enabling in situ experiments at the beamline.

Hard X-ray wavefront correction via refractive phase plates made by additive and subtractive fabrication techniques.

Modern subtractive and additive manufacturing techniques present new avenues for X-ray optics with complex shapes and patterns. Refractive phase plates acting as glasses for X-ray optics have been fabricated, and spherical aberration in refractive X-ray lenses made from beryllium has been successfully corrected. A diamond phase plate made by femtosecond laser ablation was found to improve the Strehl ratio of a lens stack with a numerical aperture (NA) of 0.88 × 10-3 at 8.2 keV from 0.1 to 0.7. A polymer phase plate made by additive printing achieved an increase in the Strehl ratio of a lens stack at 35 keV with NA of 0.18 × 10-3 from 0.15 to 0.89, demonstrating diffraction-limited nanofocusing at high X-ray energies.

Hard X-ray nano-holotomography with a Fresnel zone plate.

X-ray phase contrast nanotomography enables imaging of a wide range of samples with high spatial resolution in 3D. Near-field holography, as one of the major phase contrast techniques, is often implemented using X-ray optics such as Kirkpatrick-Baez mirrors, waveguides and compound refractive lenses. However, these optics are often tailor-made for a specific beamline and challenging to implement and align. Here, we present a near-field holography setup based on Fresnel zone plates which is fast and easy to align and provides a smooth illumination and flat field. The imaging quality of different types of Fresnel zone plates is compared in terms of the flat-field quality, the achievable resolution and exposure efficiency i.e. the photons arriving at the detector. Overall, this setup is capable of imaging different types of samples at high spatial resolution of below 100 nm in 3D with access to the quantitative phase information.

Zone plates for angle-resolved photoelectron spectroscopy providing sub-micrometre resolution in the extreme ultraviolet regime.

This article reports on the fabrication and testing of dedicated Fresnel zone plates for use at the nano-ARPES branch of the I05-ARPES beamline of Diamond Light Source to perform angle-resolved photoelectron spectroscopy with sub-micrometre resolution in real space. The aim of the design was to provide high photon flux combined with sub-micrometre spot sizes. The focusing lenses were tested with respect to efficiency and spatial resolution in the extreme ultraviolet between 50 eV and 90 eV. The experimentally determined diffraction efficiencies of the zone plates are as high as 8.6% at 80 eV, and a real-space resolution of 0.4 µm was demonstrated. Using the zone-plate-based setup, monolayer flakes of the two-dimensional semiconductor WS2 were investigated. This work demonstrates that the local electronic structure can be obtained from an area of a few micrometres across a two-dimensional heterostructure.